/**
 * 724. 寻找数组的中心下标
 */
class Solution1 {
    public int pivotIndex(int[] nums) {
        int n = nums.length;
        int[] left = new int[n], right = new int[n], ret = new int[n];
        left[0] = right[n - 1] = 0;

        for(int i = 1; i < n; i++) {
            left[i] = left[i - 1] + nums[i - 1];
        }

        for(int i = n - 2; i >= 0; i--) {
            right[i] = right[i + 1] + nums[i + 1];
        }

        for(int i = 0; i < n; i++) {
            if(left[i] == right[i]) return i;
        }

        return -1;
    }
}